1. Field Of The Invention
This invention generally relates to a substrate treatment device using a dielectric barrier discharge lamp. The invention relates especially to a device for irradiation treatment, in which a substrate and a dielectric barrier discharge lamp are moved relative to one another.
2. Description Of Related Art
JP Patent Disclosure Document HEI 2-7353(U.S. Pat. No. 4,983,881) discloses a dielectric barrier discharge lamp in which a discharge vessel is filled with a discharge gas which forms an excimer molecule and in which, by means of a dielectric barrier discharge, which is also called an ozone production discharge or a silent discharge excimer, molecules are formed, as is described in the Discharge Handbook (Elektrogesellschaft, Revised Edition), and in which vacuum UV light is emitted from the excimer molecules.
Recently, on the other hand, as a process for eliminating organic impurities and unnecessary resist which adhere to the surface of the substrate, UV/O3 treatment is carried out using the interaction of UV light and ozone without damaging the substrate.
In this UV/O3 treatment, a low pressure mercury lamp and if necessary also an ozonizer have been used. But if the above described dielectric barrier discharge lamp is used, without using an ozonizer, ozone and a high concentration of active oxygen are obtained and a device is made available where the treatment speed is greatly increased. This technology is disclosed for example in JP Patent Disclosure Document HEI 7-196303 (U.S. Pat. No. 5,510,158).
FIGS. 6(a) and 6(b) are schematic diagrams showing a treatment device using a dielectric barrier discharge lamp as one such UV/O3 treatment. A dielectric barrier discharge lamp 1, hereinafter also called a xe2x80x9cdischarge lampxe2x80x9d or a xe2x80x9clampxe2x80x9d, is located in an essentially box-shaped lamp unit 2. Vacuum UV radiation is emitted onto a substrate P via a transmission window 3 which forms one side of this lamp unit 2. The substrate P is transported in the direction of the arrow (marked black) in the drawings. When the transport is completed the irradiation of the entire substrate surface is ended. Between the transmission window 3 and the substrate P there is a gap of a few millimeters. When oxygen which is present in this gap reacts to the vacuum UV light, active oxygen and ozone are produced. Due to the mutual interaction thereof with the vacuum UV light, treatment and elimination of organic impurities or the like can be done.
FIG. 6(b) is a schematic in which the arrangement shown in FIG. 6(a) is viewed from underneath. In FIG. 6(b) the lengthwise direction of the essentially rod-shaped dielectric barrier discharge lamp 1 and the transport direction of the substrate are perpendicular to one another. Since the width X of the substrate is shorter than the length L of the emission part of the dielectric barrier discharge lamp 1, treatment in the manner of line irradiation according to the transport of the substrate P is enabled. The transmission window 3 is not shown in FIG. 6(b).
Recently however, substrates have become larger and larger in an effort to increase production efficiency. Specifically, substrates which conventionally have a size of 680 mmxc3x97880 mm have increased to a size of roughly 1000 mmxc3x971200 mm. The length of the direction perpendicular to the transport direction (X in FIG. 6(b)) therefore becomes larger than the length L of the emission portion of the discharge lamp. Only by simple transport of the substrate the entire region of the substrate surface can no longer be irradiated.
This problem could be solved perhaps by using an optical system, such as a reflector, a lens, or the like, if a general light source device were to be used, i.e., a device in which a conventional lamp, i.e., not a dielectric barrier discharge lamp, but a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, a filament lamp, or the like, is used as a light source. However, in a dielectric barrier discharge lamp, its radiant light is short, i.e., it has a wavelength of less than or equal to 200 nm (called vacuum UV light). When an optical system such as a reflector or the like is used, the problem of damage, such as degradation of the UV radiation, or the like, clearly arises. When the UV radiation is exposed to an oxygen atmosphere, it is easily absorbed. Therefore, a measure such as production of an atmosphere of an inert gas in the lamp vicinity or a similar measure is necessary. Thus, there is the difficulty of arranging a complex optical system in an inert gas atmosphere and the structural limitation that the light transmission window and the substrate must be brought extremely close to one another arise. Therefore, it is not possible to react to the enlargement of the substrate by using an optical system and a conventional lamp. This is a problem which is particular to a light source device using a dielectric barrier discharge lamp. In a low pressure mercury lamp, UV light with a wavelength of 185 nm is also emitted. In a dielectric barrier discharge lamp, UV light with shorter wavelengths of 172 nm and 126 nm is emitted. The above described damage to the optical system, the absorption of UV radiation by oxygen, and the proximity to the substrate are common problems.
It can be theoretically imagined that if the substrate length is increased, the emission part of the discharge lamp could likewise be increased. However, elongating of the discharge lamp entails a difficulty with respect to production and is not simple either with respect to maintaining uniform luminous operation in the lengthwise direction of the lamp.
This is especially true since in a dielectric barrier discharge lamp the quartz glass comprising the discharge lamp is used as a dielectric, and in the lengthwise direction, the thickness of the quartz glass and the adhesive properties of the electrodes must be made uniform. The applied voltage is also high. Therefore, enlargement of the discharge lamp is difficult in practice and raises safety issues as well.
Furthermore, a method can also be imagined in which the substrate is transported separately several times and the relationship of the arrangement between the substrate and the lamp can be changed such that the irradiation area changes with each transport. This method however sacrifices treatment time and furthermore entails the difficulty of setting of the substrate and the irradiation area for each transport.
As is shown in FIG. 7, an arrangement can be imagined in which within a lamp unit there are discharge lamps next to one another. FIG. 7 corresponds to FIG. 6(b). This arrangement makes it possible to advantageously react to a large substrate P by a simple arrangement of placing lamps next to one another.
From the standpoint of size this arrangement makes it possible to overcome the problems associated with enlargement of the substrate P. But this arrangement again causes another problem. That is, on the boundaries between the area irradiated by one discharge lamp and the area irradiated by the other discharge lamp, it is extremely difficult to unify the amount of irradiation light. Depending on the relationship of the arrangement of the discharge lamps, an area is formed which is not irradiated at all, or an area which is irradiated twice by the two discharge lamps is formed. For example, for the application of cleaning treatment to remove organic impurities, this leads to no cleaning treatment taking place when an area is formed which is not irradiated at all. In the area which is irradiated twice, cleaning treatment is still possible. But here, due to the excess irradiation of the substrate with the vacuum UV radiation the problem arises in that the substrate surface is undesirably damaged. Furthermore, under certain circumstances, the substrate surface is not uniformly treated, resulting in non-uniformity.
In treatment by direct irradiation of the substrate surface with vacuum UV light, and by using a photochemical reaction of the vacuum UV light with the substrate surface for other applications, in the area which is not irradiated a photochemical reaction does not take place, as in the above described cleaning treatment. Here, in the area irradiated twice, the unwanted treatment result is that as a consequence of the intense photochemical reaction, the substrate surface is not uniformly treated.
An exemplary object of the invention is to devise an irradiation treatment device in which a high speed uniform irradiation treatment can be achieved without damaging the substrate, even in the case in which the substrate to be treated is enlarged and exceeds the length of the rod-shaped dielectric barrier discharge lamp.
The exemplary object is achieved in a substrate treatment device using dielectric barrier discharge lamps in which the substrate is transported with respect to the dielectric barrier discharge lamps and in which the surface of the substrate is irradiated with UV light from the dielectric barrier discharge lamps. Since the length for the above described dielectric barrier discharge lamps in the lengthwise direction is less than the length in the direction perpendicular to the transport direction of the above described substrate, and since there are at least two dielectric barrier discharge lamps, there is an area of the substrate which is irradiated by one dielectric barrier discharge lamp and there is an area that is irradiated by the other dielectric barrier discharge lamp. With respect to the UV light emitted by the respective dielectric barrier discharge lamps in the overlapping area, there are light screening means which transition the effect between the two lamps.
By this arrangement, firstly, by using several rod-shaped dielectric barrier discharge lamps, it is possible to advantageously compensate for the increase in size of the substrate without enlarging the discharge lamps. Secondly, by formation of a double-irradiated area at least in one part of the substrate which is irradiated with vacuum UV light, the disadvantage associated with the boundaries of the irradiation areas can be eliminated. Thirdly, through the arrangement of the light screening means, by which the irradiation areas are changed according to the transport of the substrate with respect to this double-irradiated area of the substrate, damage to the substrate by excess irradiation can be prevented and moreover scattering of the treatment by non-uniform irradiation can be reduced.
Another exemplary object is achieved in the substrate treatment device in that instead of transporting the above described substrate in relation to the dielectric barrier discharge lamps, the above described substrate remains fixed, and the dielectric barrier discharge lamps are moved and illuminated to emit thereby performing the irradiation treatment.
The object is achieved in another version of the invention in a substrate treatment device in that the above described light screening means are arranged such that the amount of irradiation per unit of area on the substrate becomes essentially uniform after treatment.
The arrangement of the light screening means makes the amount of irradiation per unit of area on the substrate completely uniform. Thus the disadvantage of non-uniformity of treatment can be completely eliminated.
The object is achieved in another version of the invention in a substrate treatment device in that the dielectric barrier discharge lamps are located in an essentially box-shaped lamp unit, with one side provided with light transmission windows, and the respective light screening means is a light screening plate which is located in this light transmission window.